A refrigeration cycle apparatus adapted to circulate a non-azeotropic refrigerant mixture through a refrigeration cycle has been proposed (see, for example, Patent Literature 1).
Regarding refrigerants used in a refrigeration cycle apparatus, HFC-based refrigerants, such as hydrofluorocarbon (HFC)134a, R404A, R410A and R407c, which mainly consists of carbon, hydrogen and fluorine have been used widely in place of chlorine-containing refrigerants, such as chlorofluorocarbon (CFC)-12 and hydrochlorofluorocarbon (HCFC) 22 from the viewpoint of ozonosphere protection. However, use of the HFC-based refrigerants having greater global warming potential has also been avoided in response to a recent growing concern over the global environment problem. Replacement of the HFC-based refrigerants with refrigerants having smaller global warming potential (i.e., low-GWP refrigerants) has been investigated. Note that the global warming potential is a value representing a degree of greenhouse effect with the greenhouse effect of carbon dioxide being a criterion.
A strong candidate of such alternative refrigerant is hydrofluoroolefin (also referred to as fluoroalkene) (see, for example, Patent Literature 2). Hydrofluoroolefin has lower chemical stability as compared with that of the HFC-based refrigerant and thus smaller global warming potential. R410A, a HFC-based refrigerant, has the global warming potential that is about 2000 times greater than that of carbon dioxide. As compared with R410A, hydrofluoroolefin has the global warming potential that is about four times greater than that of carbon dioxide. Further, pressure level necessary for hydrofluoroolefin is advantageously the same as those of the related art HFC-based refrigerants.